Circulating decrement-deep purification method for biorefractory wastewater

Abstract

The invention belongs to the field of environmental protection, and discloses a non-biodegradable wastewater circulation decrement-deep purification method which comprises the following steps: pre-treating non-biodegradable wastewater, enabling the pre-treated wastewater to enter a multi-stage nanofiltration system, desalting nanofiltration purified water of each stage of nanofiltration system through reverse osmosis treatment, removing the nanofiltration purified water from the last stage of nanofiltration system, and recycling the non-biodegradable wastewater. The nanofiltration concentrated solution of the other stages of nanofiltration systems enters the next stage of nanofiltration system, the nanofiltration concentrated solution of the last stage of nanofiltration system is subjected to reaction precipitation treatment, and the precipitated clear solution returns to one stage of nanofiltration system in the multi-stage nanofiltration system; ammonia nitrogen and volatile organic compounds generated by pretreatment are subjected to reaction and precipitation treatment, and obtained slurry enters an oxygen cracking system and is subjected to oxygen cracking under the action of a catalyst, so that pollutants are directly converted into substances harmless to the environment; the catalyst is regenerated by washing to remove salts, and washing liquor is evaporated to obtain solid carnallite. The method has the advantages of low treatment energy consumption and no generation of membrane concentrate during treatment of the wastewater difficult to biochemically treat, and can be matched with the mainstream biochemical technology.

Description

Technical Field

[0001] The invention belongs to the field of environmental protection, and relates to a difficult-to-biochemical wastewater circulation reduction-deep purification method, which is applied to the treatment of difficult-to-biochemical wastewater. Background Art

[0002] Biochemical treatment is the mainstream process for wastewater treatment at present. It has the advantages of low operating cost and low energy consumption, and is widely used in industrial and municipal wastewater treatment. However, wastewater often contains some toxic and harmful substances that are difficult to be degraded by microorganisms, such as humic acid, organic chlorides, polycyclic compounds represented by aromatics, and other long-chain compounds. These substances are difficult to effectively remove in traditional biochemical treatment processes. Therefore, in actual application, it is usually supplemented with other treatment processes such as Fenton treatment, membrane treatment, and incineration treatment to improve the treatment effect.

[0003] Patent CN101786756A discloses a process for treating difficult-to-biochemical wastewater. The wastewater is treated by three reaction units: an ultrasonic cavitation zone, an electrochemical reaction zone, and an ultraviolet catalytic reaction zone. It can realize an efficient multi-stage deep wastewater oxidation reaction combining ultrasonic wastewater treatment method, ultraviolet light synergistic Fenton reagent oxidation treatment method, and electrochemical and its synergistic Fenton reagent oxidation treatment method. The COD concentration of the effluent is between 239 and 409 mg / L, the oxidation is not complete, and a large amount of H2O2 will be consumed. Patent CN102942270A discloses a biochemical effluent deep treatment and reuse process for coking wastewater. The wastewater is deeply treated by catalytic oxidation, flocculation sedimentation, filtration and membrane separation methods. The final effluent COD concentration is 10 mg / L and the water output is 75%. However, the membrane concentrate produced in the process still needs to be treated secondary, and the treatment process is relatively long. This method still cannot effectively dispose of some pollutants and can only be incinerated. Although the incineration method can completely decompose organic matter, the energy consumption during the incineration process is high and harmful gases are generated.

[0004] In summary, the current biochemical-assisted treatment process has problems such as high consumption of reagents, easy generation of secondary pollution, and high treatment energy consumption. It is necessary to develop low-energy, high-efficiency, and secondary-pollution-free technologies to match the mainstream technology of biochemical treatment. Summary of the invention

[0005] The present invention provides a cyclic reduction-deep purification method to address the problems of large reagent consumption, easy secondary pollution, high treatment energy consumption, etc. in existing difficult-to-biochemical wastewater treatment technologies.

[0006] The objective of the present invention is achieved through the following technical solutions:

[0007] A method for recycling and reducing the amount of difficult-to-biochemical wastewater and deeply purifying the wastewater comprises: pre-treating the difficult-to-biochemical wastewater, the pre-treated wastewater enters a multi-stage nanofiltration system, the nanofiltration purified water of each stage of the nanofiltration system is desalinated by reverse osmosis treatment, the nanofiltration concentrate of each stage of the nanofiltration system except the last stage of the nanofiltration system enters the next stage of the nanofiltration system, the last stage of the nanofiltration concentrate is subjected to reaction precipitation treatment, and the precipitated clear liquid is returned to one of the nanofiltration systems in the multi-stage nanofiltration system; the ammonia nitrogen and volatile organic matter generated by the pre-treatment and the slurry obtained by the reaction precipitation treatment enter an oxygen cracking system, and the oxygen cracking is carried out under the action of a catalyst to directly convert the pollutants into substances that are harmless to the environment; the catalyst is regenerated by washing with water to remove salts, and the washing liquid is evaporated to obtain solid impurities; no secondary pollution and membrane concentrated liquid are generated during the entire purification process.

[0008] The COD concentration of the difficult-to-biodegrade wastewater is 1000-6000 mg / L, the ammonia nitrogen concentration is 150-5000 mg / L, the suspended matter content is 10-5000 mg / L, the salt content is 2-5%, and the total amount of sodium chloride and potassium chloride accounts for at least 70% of the total amount of salt.

[0009] The biodegradable wastewater contains biodegradable organic matter, which includes but is not limited to humic acid, organic chlorides, polycyclic compounds represented by aromatics, and other long-chain compounds; the cations of the salt include but are not limited to sodium ions, potassium ions, calcium ions, and magnesium ions, and the anions include but are not limited to sulfate ions and chloride ions.

[0010] The pretreatment is at least one of a first reaction precipitation treatment and a physical analysis treatment. The concentration of suspended matter in the pretreated wastewater is ≤30 mg / L, and the concentration of ammonia nitrogen is ≤25 mg / L.

[0011] Preferably, when the suspended solids concentration of the difficult-to-biodegrade wastewater is ≤30 mg / L, the pretreatment is a physical analysis treatment, and there is no need to perform a first reaction precipitation treatment; when the suspended solids concentration of the difficult-to-biodegrade wastewater is >30 mg / L, the pretreatment is a first reaction precipitation treatment and a physical analysis treatment.

[0012] The suspended solids and some organic matter in the wastewater are removed through the first reaction precipitation treatment.

[0013] The first reaction precipitation treatment is to add precipitation aid A, precipitation aid B and pH regulator to the difficult-to-biodegrade wastewater.

[0014] The precipitation aid A is one of an iron-based aid and an aluminum-based aid; the iron-based aid is selected from polyferric sulfate, ferrous sulfate, and ferric chloride; the aluminum-based aid is selected from polyaluminum sulfate and aluminum sulfate.

[0015] The addition amount of the precipitation aid A is 0.6-1.8% of the mass of the difficult-to-biodegrade wastewater.

[0016] The precipitation aid B is one of polyamide solution, starch solution and chitosan solution with a concentration of 2-4%; the polyamide is selected from cationic polyacrylamide and anionic polyacrylamide.

[0017] The addition amount of the precipitation aid B is 0.02-0.04% of the mass of the difficult-to-biodegrade wastewater.

[0018] The pH regulator is one of calcium oxide, sodium hydroxide and potassium hydroxide.

[0019] The pH of the wastewater is adjusted to 9-12 using a pH regulator.

[0020] Ammonia nitrogen and volatile organic matter in wastewater are removed through physical analysis treatment. The ammonia nitrogen concentration in the wastewater treated by physical analysis is ≤25mg / L.

[0021] The physical analysis treatment is carried out in a physical analysis tower, which is a packed tower with a tower body temperature of 40-90° C. Air is introduced into the physical analysis tower or not.

[0022] The packing of the physical analysis tower is one or two of Raschig rings, Pall rings, theta rings, step rings, corrugated plate packing, wire mesh corrugated packing and grid packing.

[0023] Preferably, the physical analysis treatment is as follows: wastewater is pumped into the physical analysis tower from the top of the tower, air is input into the physical analysis tower from the bottom of the tower by an air compressor, the gas-liquid ratio is 500:1 to 1200:1, the wastewater passes through the physical analysis tower from top to bottom, the gas and liquid phases are fully contacted in the physical analysis tower, the gas entrains ammonia nitrogen and volatile organic matter in the wastewater and is discharged from the upper part of the physical analysis tower, and wastewater treated with physical analysis is obtained in the bottom of the physical analysis tower; or wastewater is pumped into the physical analysis tower from the top of the tower, passes through the physical analysis tower from top to bottom, and the gas containing ammonia nitrogen and volatile organic matter is discharged from the upper part of the physical analysis tower, and wastewater treated with physical analysis is obtained in the bottom of the physical analysis tower.

[0024] The water purification yield of the nanofiltration system is 85% to 98%.

[0025] In the multi-stage nanofiltration system, the membrane assembly of each stage of the nanofiltration system is a roll-type membrane assembly, and the material of the nanofiltration membrane of the roll-type membrane assembly is polyamide fiber; the filtration accuracy of each stage of the nanofiltration system is 0.001-0.003 μm, the working pressure is 0.5-2 MPa, the working temperature is 20-45°C, and the working pressure of the latter stage of the nanofiltration system is higher than the working pressure of the previous stage of the nanofiltration system.

[0026] Preferably, the working pressure of the latter nanofiltration system is higher than the working pressure of the former nanofiltration system, and the difference in working pressure is ≥0.2 MPa.

[0027] Preferably, the nanofiltration membranes of each stage of the nanofiltration system are the same, and the model of the nanofiltration membranes is NF3013-600G-30%.

[0028] The COD concentration of nanofiltration purified water in each stage of nanofiltration system is ≤60mg / L, and the ammonia nitrogen concentration is ≤20mg / L. The nanofiltration purified water in each stage of nanofiltration system is subjected to reverse osmosis treatment and desalination before meeting the discharge standards.

[0029] The reverse osmosis membrane of the reverse osmosis system used in the reverse osmosis treatment is model RO3013-600, with a pore size of 0.1nm, a working pressure of 0.5-2MPa, a working temperature of 20-45°C, and a desalination rate of 95%-99%.

[0030] The reverse osmosis treatment removes sodium chloride and potassium chloride.

[0031] The COD concentration of the concentrated liquid of the last stage of nanofiltration system is ≥15000 mg / L. The COD concentration of the concentrated liquid of the last stage of nanofiltration system is about 5 to 39 times the COD concentration of the difficult-to-biodegradable wastewater after pretreatment.

[0032] Preferably, precipitation aid A, precipitation aid B and pH regulator are added to the final nanofiltration concentrate for reaction precipitation treatment.

[0033] The precipitation aid A is one of an iron-based aid and an aluminum-based aid; the iron-based aid is selected from polyferric sulfate and ferric chloride; the aluminum-based aid is selected from polyaluminum sulfate and aluminum sulfate.

[0034] The addition amount of the precipitation aid A is 0.6-1.8% of the mass of the last stage nanofiltration concentrated liquid.

[0035] The precipitation aid B is one of polyamide solution, starch solution and chitosan solution with a concentration of 2-4%; the polyamide is selected from cationic polyacrylamide and anionic polyacrylamide.

[0036] The addition amount of the precipitation aid B is 0.02-0.04% of the mass of the last stage nanofiltration concentrated liquid.

[0037] The pH regulator is one of calcium oxide, sodium hydroxide and potassium hydroxide.

[0038] A pH regulator is used to adjust the pH of the clear liquid precipitated after the final nanofiltration concentrated liquid is subjected to reaction precipitation treatment to a value of 9 to 12.

[0039] The catalyst is an acidic molecular sieve loaded with metal oxide, the loading amount of the metal oxide is 10-35%, and it has the dual functions of cracking and oxidation; the metal oxide is one or two of vanadium oxide, copper oxide, cerium oxide, manganese oxide, and cobalt oxide; the acidic carrier is one of Y-type and β-type molecular sieves.

[0040] The temperature of the oxygen cracking is 300-500°C.

[0041] The number of the oxygen-proximate cracking reactors in the oxygen-proximate cracking system is 1 to 2; when the number of the oxygen-proximate cracking reactors in the oxygen-proximate cracking system is 2, the two oxygen-proximate cracking reactors are connected in series in sequence.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] The present invention has low treatment energy consumption when treating difficult-to-biochemical wastewater, produces no membrane concentrated liquid, and can match the mainstream biochemical technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 The present invention is a flow chart of the method for recycling reduction and deep purification of difficult-to-degrade organic wastewater. DETAILED DESCRIPTION

[0045] The technical solution of the present invention is further described below through implementation cases, but the protection scope of the present invention is not limited thereto.

[0046] Example 1

[0047] The difficult-to-biodegradable wastewater to be treated in this embodiment is the biochemical effluent of kitchen wastewater from a kitchen waste factory. The main organic pollutants contained in it are oils and humic acid, and the salts are mainly sodium chloride, potassium chloride, magnesium chloride, etc. The COD concentration of the difficult-to-biodegradable wastewater is 1100 mg / L, the ammonia nitrogen concentration is 1150 mg / L, the suspended matter content is 25 mg / L, the salt content is 2.3%, of which the total content of sodium chloride and potassium chloride is 1.8%. Due to the low content of suspended matter in the wastewater, the first reaction precipitation is not required for pretreatment.

[0048] like Figure 1 As shown in the figure, the packing of the physical decomposition tower is a metal wire mesh corrugated packing. The difficult-to-biodegrade wastewater is pumped into the physical decomposition tower from the top of the tower by a water pump, and the high-speed gas is input into the physical decomposition tower from the bottom of the tower by an air compressor. The flow rate of the difficult-to-biodegrade wastewater is controlled to be 0.2m 3 / h, the air velocity is 100m 3 / h, the gas-liquid ratio is 500:1, and the temperature of the physical analysis tower is maintained at 50°C; in the physical analysis tower, the wastewater flows from top to bottom, the gas and liquid phases are fully in contact, and the gas entrains ammonia nitrogen and volatile organic matter in the wastewater from bottom to top. The ammonia nitrogen concentration of the bottom liquid of the physical analysis tower is 12.3 mg / L, and the COD concentration is 998 mg / L.

[0049] Physical analysis: The tower kettle liquid is transported by a high-pressure pump into the first-stage nanofiltration system for first-stage nanofiltration. The membrane component of the first-stage nanofiltration system is a roll membrane component. The model of the nanofiltration membrane used in the roll membrane component is NF3013-600G-30%. The nanofiltration membrane is made of polyamide fiber. The working pressure of the first-stage nanofiltration system is 1MPa, the working temperature is 25°C, the filtration accuracy is 0.002μm, and the purified water recovery rate is 80%; the COD concentration of the first-stage nanofiltration purified water is 55.6mg / L, the ammonia nitrogen concentration is 8.4mg / L, and the total content of sodium chloride and potassium chloride is 1.69%. The first-stage nanofiltration purified water enters the reverse osmosis system for desalination. The model of the reverse osmosis membrane of the reverse osmosis system is RO3013-600, and the pore size is 0.1nm The working pressure of the reverse osmosis system is 1MPa, the working temperature is 25℃, and the total content of sodium chloride and potassium chloride in the first-level nanofiltration purified water is reduced to 0.03% after reverse osmosis treatment; the COD concentration of the first-level nanofiltration concentrate is 4283mg / L, and the first-level nanofiltration concentrate enters the second-level nanofiltration system for second-level nanofiltration. The membrane component of the second-level nanofiltration system is a roll membrane component, and the model of the nanofiltration membrane used in the roll membrane component is NF3013-600G-30%, and the nanofiltration membrane material is polyamide fiber. The working pressure of the second-level nanofiltration system is 1.5MPa, the working temperature is 25℃, the filtration accuracy is 0.002μm, and the purified water recovery rate is 80%; the COD concentration of the second-level nanofiltration purified water is 45.3mg / L, and the ammonia nitrogen concentration is 7 .3mg / L, the total content of sodium chloride and potassium chloride is 1.97%, the secondary nanofiltration purified water enters the reverse osmosis system for desalination, the reverse osmosis membrane model of the reverse osmosis system is RO3013-600, the pore size is 0.1nm, the working pressure of the reverse osmosis system is 1MPa, the working temperature is 25℃, the total content of sodium chloride and potassium chloride in the secondary nanofiltration purified water is reduced to 0.04% after reverse osmosis treatment; the COD concentration of the secondary nanofiltration concentrate is 19860mg / L, the secondary nanofiltration concentrate enters the tertiary nanofiltration system for tertiary nanofiltration, the membrane assembly of the tertiary nanofiltration system is a roll membrane assembly, the model of the nanofiltration membrane used in the roll membrane assembly is NF3013-600G-30%, the nanofiltration membrane material is polyamide fiber, the tertiary nanofiltration system The working pressure is 2MPa, the working temperature is 25℃, the filtration accuracy is 0.002μm, and the purified water recovery rate is 50%; the COD concentration of the tertiary nanofiltration purified water is 36.8mg / L, the ammonia nitrogen concentration is 6.4mg / L, and the total content of sodium chloride and potassium chloride is 4.7%. The tertiary nanofiltration purified water enters the reverse osmosis system for desalination. The model of the reverse osmosis membrane of the reverse osmosis system is RO3013-600, and the pore size is 0.1nm. The working pressure of the reverse osmosis system is 1MPa, and the working temperature is 25℃. After the reverse osmosis treatment, the total content of sodium chloride and potassium chloride in the tertiary nanofiltration purified water is reduced to 0.07%; the COD concentration of the tertiary nanofiltration concentrate is 38430mg / L, and the total water production rate of the nanofiltration system purified water is 98%.0.0024 kg of calcium oxide, 0.2 kg of ferrous sulfate and 0.006 kg of 2% cationic polyacrylamide solution were added to every 20 kg of tertiary nanofiltration concentrated liquid. Calcium oxide, ferrous sulfate and 2% cationic polyacrylamide solution were added to the tertiary nanofiltration concentrated liquid for reaction precipitation treatment. The COD concentration of the precipitated clear liquid was 20136 mg / L and the pH was 9. The precipitated clear liquid was returned to the tertiary nanofiltration system for nanofiltration.

[0050] The slurry obtained by the reaction precipitation treatment of the tertiary nanofiltration concentrate, the ammonia nitrogen discharged from the top of the physical analysis tower and the volatile organic matter enter the single-stage oxygen cracking reactor for oxygen cracking. The catalyst loaded in the reactor is manganese oxide-cerium oxide / β molecular sieve catalyst (manganese oxide loading is 10wt%, cerium oxide loading is 10wt%), and the operating temperature of the oxygen cracking reactor is 450°C; the concentration of non-methane total hydrocarbons discharged from the oxygen cracking reactor is 4.2mg / m 3 The catalyst is regenerated by washing with water to remove salts, and the washing liquid is evaporated to obtain a mixture of solid magnesium chloride, calcium chloride and magnesium sulfate (TOC content is 3.8 mg / kg).

[0051] Example 2

[0052] The difficult-to-biochemical wastewater to be treated in this embodiment is the biochemical effluent of a factory's landfill leachate, and the main organic pollutants are humic acid, aromatic compounds, etc., and the salts are mainly sodium chloride, potassium chloride, magnesium chloride, sodium sulfate, etc.; the COD concentration of the difficult-to-biochemical wastewater is 5800 mg / L, the ammonia nitrogen concentration is 180 mg / L, the suspended matter concentration is 4000 mg / L, the salt content is 3%, of which the total content of sodium chloride and potassium chloride is 2.1%.

[0053] 0.7kg calcium oxide, 16.2kg polyferric sulfate and 0.2kg cationic polyacrylamide solution with a mass fraction of 2% were added to 1000kg of difficult-to-biodegrade wastewater for the first reaction precipitation treatment to remove suspended solids and some organic matter in the organic wastewater. The pH of the difficult-to-degrade organic wastewater after reaction precipitation treatment was 9, the COD concentration was 3200mg / L, the ammonia nitrogen concentration was 180mg / L, and the suspended solid concentration was 20mg / L.

[0054] The fillers of the physical decomposition tower are Raschig rings and θ rings, and the ratio of the two is 1:1; the difficult-to-degrade organic wastewater treated by reaction precipitation is pumped into the physical decomposition tower from the top of the tower by a water pump, and the temperature of the physical decomposition tower is maintained at 85°C. Under the action of heating, ammonia nitrogen and volatile organic matter escape, and the ammonia nitrogen concentration of the bottom liquid of the physical decomposition tower is 15mg / L, and the COD concentration is 3049mg / L.

[0055] The liquid in the kettle of the physical analysis tower is transported by a high-pressure pump into the first-stage nanofiltration system for first-stage nanofiltration. The membrane assembly of the first-stage nanofiltration system is a spiral membrane assembly. The model of the nanofiltration membrane used in the spiral membrane assembly is NF3013-600G-30%. The material of the nanofiltration membrane is polyamide fiber. The working pressure of the first-stage nanofiltration system is 0.8MPa, the working temperature is 25℃, the filtration accuracy is 0.002μm, and the purified water recovery rate is 50%; the COD concentration of the first-stage nanofiltration purified water is 53.7mg / L, the ammonia nitrogen concentration is 11.6mg / L, and the total content of sodium chloride and potassium chloride is 2.94%. The first-stage nanofiltration purified water enters the reverse osmosis system for desalination. The model of the reverse osmosis membrane of the reverse osmosis system is RO3013-600, and the pore size is 0. 1nm, the working pressure of the reverse osmosis system is 1MPa, the working temperature is 25℃, and the total content of sodium chloride and potassium chloride in the first-level nanofiltration purified water is reduced to 0.03% after reverse osmosis treatment; the COD concentration of the first-level nanofiltration concentrate is 5879mg / L, and the first-level nanofiltration concentrate enters the second-level nanofiltration system for second-level nanofiltration. The membrane component of the second-level nanofiltration system is a roll membrane component, and the model of the nanofiltration membrane used in the roll membrane component is NF3013-600G-30%, and the material of the nanofiltration membrane is polyamide fiber. The working pressure of the second-level nanofiltration system is 1MPa, the working temperature is 25℃, the filtration accuracy is 0.002μm, and the purified water recovery rate is 50%; the COD concentration of the second-level nanofiltration purified water is 49.6mg / L, and the ammonia nitrogen concentration The total content of sodium chloride and potassium chloride is 10.3 mg / L, and the total content of sodium chloride and potassium chloride is 1.76%. The secondary nanofiltration purified water enters the reverse osmosis system for desalination. The model of the reverse osmosis membrane of the reverse osmosis system is RO3013-600, the pore size is 0.1 nm, the working pressure of the reverse osmosis system is 1 MPa, and the working temperature is 25 ° C. After the secondary nanofiltration purified water is treated with reverse osmosis, the total content of sodium chloride and potassium chloride is reduced to 0.03%; the COD concentration of the secondary nanofiltration concentrate is 10149 mg / L, and the secondary nanofiltration concentrate enters the tertiary nanofiltration system for tertiary nanofiltration. The membrane assembly of the tertiary nanofiltration system is a roll membrane assembly. The model of the nanofiltration membrane used in the roll membrane assembly is NF3013-600G-30%. The material of the nanofiltration membrane is polyamide fiber, and the working The pressure is 1.5MPa, the working temperature is 25℃, the filtration accuracy is 0.002μm, and the purified water recovery rate is 40%; the COD concentration of the tertiary nanofiltration purified water is 46.7mg / L, the ammonia nitrogen concentration is 8.5mg / L, and the total content of sodium chloride and potassium chloride is 1.32%. The tertiary nanofiltration purified water enters the reverse osmosis system for desalination. The model of the reverse osmosis membrane of the reverse osmosis system is RO3013-600, with a pore size of 0.1nm. The working pressure of the reverse osmosis system is 1MPa, and the working temperature is 25℃. After the reverse osmosis treatment, the total content of sodium chloride and potassium chloride in the tertiary nanofiltration purified water is reduced to 0.02%; the COD concentration of the tertiary nanofiltration concentrate is 15384mg / L, and the total water production rate of the nanofiltration system purified water is 85%.According to the ratio of 0.067kg potassium hydroxide, 0.915kg aluminum sulfate and 0.04kg 3% starch colloid solution per 150kg tertiary nanofiltration concentrated liquid, potassium hydroxide, aluminum sulfate and 3% starch colloid solution were added to 150kg tertiary nanofiltration concentrated liquid for second reaction precipitation treatment. The COD concentration of the precipitated clear liquid was 8641mg / L and the pH was 11. The precipitated clear liquid was returned to the tertiary nanofiltration system for nanofiltration treatment.

[0056] The slurry obtained from the two reaction precipitation treatments, the ammonia nitrogen discharged from the top of the physical analysis tower and the volatile organic matter enter a two-stage oxygen cracking reactor composed of two oxygen cracking reactors connected in series for oxygen cracking. The catalysts loaded in the two oxygen cracking reactors are vanadium oxide-copper oxide / Y molecular sieve catalysts (the loading amount of vanadium oxide is 15wt%, and the loading amount of copper oxide is 10wt%). The operating temperature of the two oxygen cracking reactors is 500°C. The gas discharged from the first oxygen cracking reactor enters the second oxygen cracking reactor. The concentration of non-methane total hydrocarbons discharged from the second oxygen cracking reactor is 6.8mg / m 3 The purified gas; the catalyst is regenerated by washing with water to remove salts, and the washing liquid is evaporated to obtain a mixture of solid magnesium chloride and magnesium sulfate (TOC content is 4.7 mg / kg).

[0057] Example 3

[0058] The difficult-to-biochemical wastewater to be treated in this embodiment is the biochemical effluent of a factory's landfill leachate, and the main organic pollutants are humic acid, aromatic compounds and long-chain compounds, and the salts are mainly sodium chloride, potassium chloride, magnesium chloride, etc.; the COD concentration of the difficult-to-biochemical wastewater is 3600 mg / L, the ammonia nitrogen concentration is 4500 mg / L, the suspended matter concentration is 1200 mg / L, and the salt content is 4.8%, of which the total content of sodium chloride and potassium chloride is 3.5%.

[0059] 4kg of sodium hydroxide, 14.8kg of polyaluminum sulfate and 0.2kg of 2% cationic polyacrylamide solution were added to 1000kg of difficult-to-biodegrade wastewater for the first reaction precipitation treatment to remove suspended solids and some organic matter in the difficult-to-biodegrade wastewater. The pH of the difficult-to-degrade organic wastewater after reaction precipitation treatment was 12, the COD concentration was 2000mg / L, the ammonia nitrogen concentration was 4500mg / L, and the suspended solid concentration was 10mg / L.

[0060] The packing in the physical decomposition tower is Raschig ring and Ball ring, and the ratio of the two is 1:1. The difficult-to-biochemical wastewater treated by reaction precipitation is pumped into the physical decomposition tower from the top of the tower by a water pump, and the high-speed gas is input into the physical decomposition tower from the bottom of the tower by an air compressor. The flow rate of the wastewater is controlled to be 0.2m 3 / h, the air velocity is 200m 3 / h, gas-liquid ratio 1000:1, maintaining the temperature of the physical analysis tower at 65°C, the gas entrains ammonia nitrogen and volatile organic matter in the wastewater from bottom to top, the ammonia nitrogen concentration of the physical analysis tower bottom liquid is 10.2 mg / L, and the COD concentration is 1860 mg / L.

[0061] Physical analysis: The tower reactor liquid is transported by a high-pressure pump into the first-stage nanofiltration system for first-stage nanofiltration. The membrane component of the first-stage nanofiltration system is a roll membrane component. The model of the nanofiltration membrane used in the roll membrane component is NF3013-600G-30%. The material of the nanofiltration membrane is polyamide fiber. The working pressure of the first-stage nanofiltration system is 1MPa, the working temperature is 25℃, the filtration accuracy is 0.002μm, and the purified water recovery rate is 80%; the COD concentration of the first-stage nanofiltration purified water is 52.8mg / L, the ammonia nitrogen concentration is 13.9mg / L, and the total content of sodium chloride and potassium chloride is 3.06%. The first-stage nanofiltration purified water enters the reverse osmosis system for desalination. The model of the reverse osmosis membrane of the reverse osmosis system is RO3013-600, and the pore size is 0.1nm, the working pressure of the reverse osmosis system is 1MPa, the working temperature is 25℃, and the total content of sodium chloride and potassium chloride in the first-level nanofiltration purified water is reduced to 0.03% after reverse osmosis treatment; the first-level nanofiltration concentrate enters the second-level nanofiltration system for second-level nanofiltration, and the membrane component of the second-level nanofiltration system is a roll membrane component. The model of the nanofiltration membrane used in the roll membrane component is NF3013-600G-30%, and the material of the nanofiltration membrane is polyamide fiber. The working pressure of the second-level nanofiltration system is 1.6MPa, the working temperature is 25℃, the filtration accuracy is 0.002μm, and the purified water recovery rate is 60%; the COD concentration of the second-level nanofiltration purified water is 46.9mg / L, the ammonia nitrogen concentration is 8.6mg / L, and the sodium chloride and potassium chloride concentrations are 0.03% and 0.01nm, respectively. The total content of potassium chloride is 6.13%. The secondary nanofiltration purified water enters the reverse osmosis system for desalination. The model of the reverse osmosis membrane of the reverse osmosis system is RO3013-600, the pore size is 0.1nm, the working pressure of the reverse osmosis system is 1MPa, the working temperature is 25℃, and the total content of sodium chloride and potassium chloride in the secondary nanofiltration purified water is reduced to 0.08% after reverse osmosis treatment; the COD concentration of the secondary nanofiltration concentrate is 12100mg / L, and the secondary nanofiltration concentrate enters the tertiary nanofiltration system for tertiary nanofiltration. The membrane assembly of the tertiary nanofiltration system is a roll membrane assembly, and the model of the nanofiltration membrane used in the roll membrane assembly is NF3013-600G-30%, the material of the nanofiltration membrane is polyamide fiber, and the working pressure of the tertiary nanofiltration system is 1000mg / L. The pressure is 2MPa, the working temperature is 25℃, the filtration accuracy is 0.002μm, and the purified water recovery rate is 50%; the COD concentration of the three-stage nanofiltration purified water is 38.9mg / L, the ammonia nitrogen concentration is 5.4mg / L, and the total content of sodium chloride and potassium chloride is 5.52%. The three-stage nanofiltration purified water enters the reverse osmosis system for desalination. The model of the reverse osmosis membrane of the reverse osmosis system is RO3013-600, the pore size is 0.1nm, the working pressure of the reverse osmosis system is 1MPa, and the working temperature is 25℃. After reverse osmosis treatment, the total content of sodium chloride and potassium chloride in the three-stage nanofiltration purified water is reduced to 0.06%; the COD concentration of the three-stage nanofiltration concentrate is 21310mg / L, and the total water production rate of the nanofiltration system purified water is 96%.According to the formula of adding 0.005kg of sodium hydroxide, 0.4kg of ferric chloride and 0.008kg of 4% anionic polyacrylamide solution to every 40kg of tertiary nanofiltration concentrated liquid, sodium hydroxide, ferric chloride and 4% anionic polyacrylamide solution were added to the tertiary nanofiltration concentrated liquid for the second reaction precipitation treatment. The COD concentration of the precipitated clear liquid was 10980mg / L and the pH was 10. The precipitated clear liquid was returned to the tertiary nanofiltration system for nanofiltration treatment.

[0062] The slurry, ammonia nitrogen and volatile organic matter obtained from the two reaction precipitation treatments enter the single-stage oxygen cracking reactor for oxygen cracking. The catalyst loaded in the reactor is copper oxide / Y molecular sieve catalyst (the loading amount of copper oxide is 35wt%), and the operating temperature of the reactor is 400°C. The concentration of non-methane total hydrocarbons discharged from the oxygen cracking reactor is 8.6mg / m 3 The catalyst is regenerated by washing with water to remove salts, and the washing liquid is evaporated to obtain a solid mixture of calcium chloride and magnesium chloride (TOC content is 6.9 mg / kg).

Claims

1. A method for recycling and reducing the amount of difficult-to-biodegrade wastewater and deep purification, characterized in that: include: The difficult-to-biochemical wastewater is pretreated, and the pretreated wastewater enters a multi-stage nanofiltration system. The nanofiltration purified water of each nanofiltration system is desalinated by reverse osmosis treatment. Except for the last nanofiltration system, the nanofiltration concentrate of each other nanofiltration system enters the next nanofiltration system. The last nanofiltration concentrate is subjected to reaction precipitation treatment, and the precipitated clear liquid is returned to one of the nanofiltration systems in the multi-stage nanofiltration system; the ammonia nitrogen and volatile organic matter generated by the pretreatment and the slurry obtained by the reaction precipitation treatment enter the oxygen cracking system, and oxygen cracking is carried out under the action of the catalyst to directly convert the pollutants into substances that are harmless to the environment; the catalyst is regenerated by removing salts through water washing, and the washing liquid is evaporated to obtain solid impurities.

2. The method for recycling and reducing the amount of difficult-to-biochemical wastewater and deeply purifying it according to claim 1, characterized in that: The COD concentration of the difficult-to-biodegrade wastewater is 1000-6000 mg / L, the ammonia nitrogen concentration is 150-5000 mg / L, the suspended matter content is 10-5000 mg / L, the salt content is 2-5%, and the total amount of sodium chloride and potassium chloride accounts for at least 70% of the total amount of salt; the difficult-to-biodegrade wastewater contains biodegradable organic matter.

3. The method for recycling and reducing the amount of difficult-to-biochemical wastewater and deeply purifying it according to claim 1, characterized in that: The pretreatment is at least one of a first reaction precipitation treatment and a physical analysis treatment. The concentration of suspended matter in the pretreated wastewater is ≤30 mg / L, and the concentration of ammonia nitrogen is ≤25 mg / L.

4. The method for recycling and reducing the amount of difficult-to-biochemical wastewater and deeply purifying it according to claim 1, characterized in that: When the suspended solids concentration of the difficult-to-biodegrade wastewater is ≤30 mg / L, the pretreatment is a physical analysis treatment; when the suspended solids concentration of the difficult-to-biodegrade wastewater is >30 mg / L, the pretreatment is a first reaction precipitation treatment and a physical analysis treatment.

5. The method for circulating reduction and deep purification of difficult-to-biochemical wastewater according to claim 3 or 4, characterized in that: The first reaction precipitation treatment is to add precipitation aid A, precipitation aid B and pH regulator to the difficult-to-biodegrade wastewater; The precipitation aid A is one of an iron-based aid and an aluminum-based aid; the iron-based aid is selected from polyferric sulfate, ferrous sulfate, and ferric chloride; the aluminum-based aid is selected from polyaluminum sulfate and aluminum sulfate; The addition amount of the precipitation aid A is 0.6-1.8% of the mass of the difficult-to-biodegrade wastewater; The precipitation aid B is one of a polyamide solution, a starch solution, and a chitosan solution with a concentration of 2 to 4%; the polyamide is selected from cationic polyacrylamide and anionic polyacrylamide; The addition amount of the precipitation aid B is 0.02-0.04% of the mass of the difficult-to-biodegrade wastewater; The pH regulator is one of calcium oxide, sodium hydroxide and potassium hydroxide; The pH of the wastewater is adjusted to 9-12 using a pH regulator.

6. The method for circulating reduction and deep purification of difficult-to-biochemical wastewater according to claim 3 or 4, characterized in that: The physical analysis treatment is carried out in a physical analysis tower, which is a packed tower with a tower body temperature of 40-90° C. Air is introduced into the physical analysis tower or not.

7. The method for recycling and reducing the amount of difficult-to-biodegrade wastewater and deeply purifying it according to claim 6, characterized in that: The physical analysis treatment is as follows: wastewater is pumped into the physical analysis tower from the top of the tower, air is input into the physical analysis tower from the bottom of the tower by an air compressor, the gas-liquid ratio is 500:1-1200:1, wastewater passes through the physical analysis tower from top to bottom, gas and liquid phases are fully contacted in the physical analysis tower, ammonia nitrogen and volatile organic matter entrained in the wastewater are discharged from the upper part of the physical analysis tower, and wastewater treated by physical analysis is obtained in the bottom of the physical analysis tower; or wastewater is pumped into the physical analysis tower from the top of the tower, passes through the physical analysis tower from top to bottom, and gas containing ammonia nitrogen and volatile organic matter is discharged from the upper part of the physical analysis tower, and wastewater treated by physical analysis is obtained in the bottom of the physical analysis tower.

8. The method for recycling and reducing the amount of difficult-to-biochemical wastewater and deeply purifying it according to claim 1, characterized in that: In the multi-stage nanofiltration system, the membrane assembly of each stage of the nanofiltration system is a roll-type membrane assembly, and the material of the nanofiltration membrane of the roll-type membrane assembly is polyamide fiber; the filtration accuracy of each stage of the nanofiltration system is 0.001-0.003 μm, the working pressure is 0.5-2 MPa, the working temperature is 20-45°C, and the working pressure of the latter stage of the nanofiltration system is higher than the working pressure of the previous stage of the nanofiltration system; The reverse osmosis membrane model of the reverse osmosis system used in the reverse osmosis treatment is RO3013-600, the working pressure of the reverse osmosis treatment is 0.5-2MPa, and the working temperature is 20-45°C.

9. The method for recycling and reducing the amount of difficult-to-biochemical wastewater and deeply purifying it according to claim 1, characterized in that: Adding precipitation aid A, precipitation aid B and pH regulator to the last stage nanofiltration concentrate for reaction precipitation treatment; The precipitation aid A is one of an iron-based aid and an aluminum-based aid; the iron-based aid is selected from polyferric sulfate and ferric chloride; the aluminum-based aid is selected from polyaluminum sulfate and aluminum sulfate; The addition amount of the precipitation aid A is 0.6-1.8% of the mass of the last stage nanofiltration concentrate; The precipitation aid B is one of a polyamide solution, a starch solution, and a chitosan solution with a concentration of 2 to 4%; the polyamide is selected from cationic polyacrylamide and anionic polyacrylamide; The addition amount of the precipitation aid B is 0.02-0.04% of the mass of the final nanofiltration concentrate; The pH regulator is one of calcium oxide, sodium hydroxide and potassium hydroxide; A pH regulator is used to adjust the pH of the clear liquid precipitated after the final nanofiltration concentrated liquid is subjected to reaction precipitation treatment to a value of 9 to 12.

10. The method for recycling and reducing the amount of difficult-to-biodegrade wastewater and deeply purifying it according to claim 1, characterized in that: The catalyst is an acidic molecular sieve loaded with metal oxide, the loading amount of the metal oxide is 10-35%, and it has the dual functions of cracking and oxidation; the metal oxide is one or two of vanadium oxide, copper oxide, cerium oxide, manganese oxide, and cobalt oxide; the acidic carrier is one of Y-type and β-type molecular sieves; the temperature of oxygen cracking is 300-500°C.

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